diff --git a/Data/HashMap/Array.hs b/Data/HashMap/Array.hs
index 0149da4d..ccdcf9dd 100644
--- a/Data/HashMap/Array.hs
+++ b/Data/HashMap/Array.hs
@@ -43,6 +43,7 @@ module Data.HashMap.Array
       -- * Folds
     , foldl'
     , foldr
+    , foldlM'
 
     , thaw
     , map
@@ -418,6 +419,18 @@ foldl' f = \ z0 ary0 -> go ary0 (length ary0) 0 z0
             (# x #) -> go ary n (i+1) (f z x)
 {-# INLINE foldl' #-}
 
+foldlM' :: Monad m => (b -> a -> m b) -> b -> Array a -> m b
+foldlM' f = \ z0 ary0 -> go ary0 (length ary0) 0 z0
+  where
+    go ary n i !z
+        | i >= n = return z
+        | otherwise
+        = case index# ary i of
+            (# x #) -> do
+              fzx <- f z x
+              go ary n (i+1) fzx
+{-# INLINE foldlM' #-}              
+
 foldr :: (a -> b -> b) -> b -> Array a -> b
 foldr f = \ z0 ary0 -> go ary0 (length ary0) 0 z0
   where
diff --git a/Data/HashMap/Base.hs b/Data/HashMap/Base.hs
index 553d2b3a..d6b28f54 100644
--- a/Data/HashMap/Base.hs
+++ b/Data/HashMap/Base.hs
@@ -58,6 +58,7 @@ module Data.HashMap.Base
       -- * Folds
     , foldl'
     , foldlWithKey'
+    , foldlWithKeyM'
     , foldr
     , foldrWithKey
 
@@ -1551,6 +1552,17 @@ foldlWithKey' f = go
     go z (Collision _ ary)     = A.foldl' (\ z' (L k v) -> f z' k v) z ary
 {-# INLINE foldlWithKey' #-}
 
+-- | /O(n)/ Monadic version of 'foldlWithKey''.
+foldlWithKeyM' :: Monad m => (a -> k -> v -> m a) -> a -> HashMap k v -> m a
+foldlWithKeyM' f = go
+  where
+    go !z Empty                = return z
+    go z (Leaf _ (L k v))      = f z k v
+    go z (BitmapIndexed _ ary) = A.foldlM' go z ary
+    go z (Full ary)            = A.foldlM' go z ary
+    go z (Collision _ ary)     = A.foldlM' (\ z' (L k v) -> f z' k v) z ary
+{-# INLINE foldlWithKeyM' #-}    
+
 -- | /O(n)/ Reduce this map by applying a binary operator to all
 -- elements, using the given starting value (typically the
 -- right-identity of the operator).
diff --git a/Data/HashMap/Lazy.hs b/Data/HashMap/Lazy.hs
index c7306350..7362c8a8 100644
--- a/Data/HashMap/Lazy.hs
+++ b/Data/HashMap/Lazy.hs
@@ -70,6 +70,7 @@ module Data.HashMap.Lazy
       -- * Folds
     , foldl'
     , foldlWithKey'
+    , foldlWithKeyM'
     , foldr
     , foldrWithKey
 
diff --git a/Data/HashMap/Strict.hs b/Data/HashMap/Strict.hs
index 3af68b7f..1bf87929 100644
--- a/Data/HashMap/Strict.hs
+++ b/Data/HashMap/Strict.hs
@@ -69,6 +69,7 @@ module Data.HashMap.Strict
       -- * Folds
     , foldl'
     , foldlWithKey'
+    , foldlWithKeyM'
     , foldr
     , foldrWithKey
 
diff --git a/Data/HashMap/Strict/Base.hs b/Data/HashMap/Strict/Base.hs
index 890d18ff..cc8122e6 100644
--- a/Data/HashMap/Strict/Base.hs
+++ b/Data/HashMap/Strict/Base.hs
@@ -71,6 +71,7 @@ module Data.HashMap.Strict.Base
       -- * Folds
     , foldl'
     , foldlWithKey'
+    , foldlWithKeyM' 
     , HM.foldr
     , foldrWithKey